10-23-2016, 06:58 PM
Quote:Then you do not calculate correctly, using a wonky formula.
Nope. When you work with magnification, you get the exact resulting FL.
I remember now what I did as well. I had a few photographs of tape measures across the entire viewfield, photographed at the above distances. In short, based on magnification and focusing distance (from exif), knowing the sensor width, and knowing the tape length in view in the image, it is then very easy to calculate the resulting FLs.
For all intents and purposes, my method is a very practical one, and it works. With magnification you do not need to know the nodes anyway, one can calculate the resulting FL purely based on focusing distance, image size, object size, and magnification.
Kind regards, Wim
Gear: Canon EOS R with 3 primes and 2 zooms, 4 EF-R adapters, Canon EOS 5 (analog), 9 Canon EF primes, a lone Canon EF zoom, 2 extenders, 2 converters, tubes; Olympus OM-D 1 Mk II & Pen F with 12 primes, 6 zooms, and 3 Metabones EF-MFT adapters ....